The present invention relates to a fire-retardant, foam-forming composition for coating substrates. This composition comprises foam-forming, gas-evolving and/or chain-terminating additives which have an endothermic reaction at elevated temperatures, and/or fillers and an epoxide resin as a binder, which has been cured with an amine curing agent.
Epoxide resin compositions which contain epoxide resins, as well as compounds of phosphoric acid and/or nitrogen containing compounds and, if appropriate, additionally contain blowing agents, such as starch or pentaerythritol, are known. The function of the fire-retardant additives is to produce, when heated, a foam structure which has a thermally insulating effect, particularly if the foam structure has been carbonized. If the additives contain more than about 20 mole % of nitrogen and/or phosphorus and decompose at temperatures from 100.degree. to 400.degree. C. and are present in an amount of 30 to 70% by weight, relative to the weight of epoxide resin and curing agent, gaseous nitrogen and fire-retardant phosphorus compounds are liberated on heating, as a result of which particularly advantageous fire-retardant protective coatings may be produced. Compositions of this kind are disclosed, for example, in German Offenlegungsschrift 2,704,275.
Other attempts to impart fire-retardant properties to epoxide resin compositions include the addition of antimony compounds, phosphorus compounds, boron compounds, compounds which split off chlorine or bromine, organic tin salts and salts of calcium, cadmium, lead, magnesium and ammonium. It has been found, however, that, if these substances are used either individually or in combination, it is not possible to achieve fire protection for an adequate period, particularly in the case of buildings or other structures which must be protected from fire. In particular, values of the category F 30 (according to Fire Protection Standard DIN 4102) are only achieved with difficulty using supplementary heating. These epoxide resin compositions crack open prematurely on the surface, particularly if supplementary heating in an oven for small conflagrations is used, and deep cracks are formed, through which the heat rapidly reaches the article or the substrate which is intended to be protected. A similar effect is already achieved as a result of the supplementary heating.
The search has continued for improved flame-retardant, foam-forming compositions for coating substrates. This invention was made as a result of that search.